156 damentals Industri I d d s ia l l Rob bo tics s Fu un Copyright Goodheart-Willcox Co., Inc. Copyright Goodheart-Willcox Co., Inc. Activity 67- Electromagnetic Relays Objectives Relays are electromagnetic switches and are excellent examples of how a mag- netic fi eld attracts a magnetic material. These devices contain a coil that creates an fi electromagnetic fi eld an armature, which is constructed of a magnetic material fi attracted by the coil and a number of contacts or switches that open or close when the magnetic field attracts the armature. fi In this activity, you will study the electromagnetic characteristics of a relay. Relays are a popular type of control device that might be used with robotic systems. Equipment and Materials: • Multicontact relay. • 6V lamp with socket. • Variable dc power supply. • Resistor—1 kΩ. • 6V battery. • Connecting wires. • Multimeter. Procedure 1. Prepare the multimeter to measure resistance. Measure and record the resistance of the relay coil. 2. Using the multimeter, determine how many normally open and normally closed contacts are used with your relay.